The rates desks are generally quite spot on with these things IME. I'd trust them over a lot of the new staff at the ATW desk.

My reading of the applicable fare rule ("and/or travel originating in") indicates that you can indeed ticket that itinerary in the US at the UK base fare.

Just noticed that the EU exemption from "higher of 2" pricing has been v slightly modified to an ECAA exemption now. Definition of ECAA here: http://en.wikipedia.org/wiki/Europea..._Aviation_Area ;nothing much has changed unless anyone was intending to issue the ticket from an EU state that isn't signatory to the ECAA.